Add NoLog option on testcli.Runner (#2183)

## Changes
Setting Verbose=false on testcli.Runner disables all logging related to
running process (stdout, stderr, error, args).

I'm using this in #2184 where I'm using testcli runner to run acceptance
tests and seeing all output is not useful.

## Tests
Manually inspecting test output in #2184

internal/testcli/runner.go

@@ -39,6 +39,8 @@ type Runner struct {
 	StderrLines <-chan string
 
 	errch <-chan error
+
+	Verbose bool
 }
 
 func consumeLines(ctx context.Context, wg *sync.WaitGroup, r io.Reader) <-chan string {
@@ -139,7 +141,9 @@ func (r *Runner) RunBackground() {
 	go func() {
 		err := root.Execute(ctx, cli)
 		if err != nil {
-			r.Logf("Error running command: %s", err)
+			if r.Verbose {
+				r.Logf("Error running command: %s", err)
+			}
 		}
 
 		// Close pipes to signal EOF.
@@ -154,7 +158,9 @@ func (r *Runner) RunBackground() {
 			// Make a copy of the buffer such that it remains "unread".
 			scanner := bufio.NewScanner(bytes.NewBuffer(r.stdout.Bytes()))
 			for scanner.Scan() {
-				r.Logf("[databricks stdout]: %s", scanner.Text())
+				if r.Verbose {
+					r.Logf("[databricks stdout]: %s", scanner.Text())
+				}
 			}
 		}
 
@@ -162,7 +168,9 @@ func (r *Runner) RunBackground() {
 			// Make a copy of the buffer such that it remains "unread".
 			scanner := bufio.NewScanner(bytes.NewBuffer(r.stderr.Bytes()))
 			for scanner.Scan() {
-				r.Logf("[databricks stderr]: %s", scanner.Text())
+				if r.Verbose {
+					r.Logf("[databricks stderr]: %s", scanner.Text())
+				}
 			}
 		}
 
@@ -196,18 +204,24 @@ func (r *Runner) Run() (bytes.Buffer, bytes.Buffer, error) {
 	cli.SetErr(&stderr)
 	cli.SetArgs(r.args)
 
-	r.Logf("  args: %s", strings.Join(r.args, ", "))
+	if r.Verbose {
+		r.Logf("  args: %s", strings.Join(r.args, ", "))
+	}
 
 	err := root.Execute(ctx, cli)
 	if err != nil {
-		r.Logf(" error: %s", err)
+		if r.Verbose {
+			r.Logf(" error: %s", err)
+		}
 	}
 
 	if stdout.Len() > 0 {
 		// Make a copy of the buffer such that it remains "unread".
 		scanner := bufio.NewScanner(bytes.NewBuffer(stdout.Bytes()))
 		for scanner.Scan() {
-			r.Logf("stdout: %s", scanner.Text())
+			if r.Verbose {
+				r.Logf("stdout: %s", scanner.Text())
+			}
 		}
 	}
 
@@ -215,7 +229,9 @@ func (r *Runner) Run() (bytes.Buffer, bytes.Buffer, error) {
 		// Make a copy of the buffer such that it remains "unread".
 		scanner := bufio.NewScanner(bytes.NewBuffer(stderr.Bytes()))
 		for scanner.Scan() {
-			r.Logf("stderr: %s", scanner.Text())
+			if r.Verbose {
+				r.Logf("stderr: %s", scanner.Text())
+			}
 		}
 	}
 
@@ -275,8 +291,9 @@ func NewRunner(t testutil.TestingT, ctx context.Context, args ...string) *Runner
 	return &Runner{
 		TestingT: t,
 
-		ctx:  ctx,
-		args: args,
+		ctx:     ctx,
+		args:    args,
+		Verbose: true,
 	}
 }